For use in certain medical applications, such as laser arthroscopy, in which an optical fiber conveying laser energy from a laser is introduced through a tiny puncture into the knee, shoulder, hip, ankle, elbow or other joint to treat damage or disease in the joint, the optical fiber is disposed within a metal tube or cannula, usually made of surgical grade stainless steel. The distal end of the optical fiber is usually positioned at or just within the distal end of the metal cannula.
In use, due to back-scatter of light energy from the target tissue, particularly if a dense material, such as bone, is being exposed to laser energy, the protective buffer coating and cladding of the optical fiber can be destroyed and the optical fiber itself can be eroded. Laser energy can escape from the side walls of an eroded optical fiber in an undesired direction and, as the optical fiber is eroded further back into the metal cannula, energy is emitted at aberrant angles from the deformed distal end of the optical fiber, which can strike the distal end portion of the metal cannula. At energy levels sufficient to vaporize cartilage or bone, when struck by such aberrant beams of laser energy, the metal cannula becomes hot and can emit sparks as the metal is vaporized. The deposition of tiny bits of metal in the body can cause adverse effects.
Electropolishing the interior of the distal end of the metal cannula may not prevent laser energy from damaging the metal cannula. As a result, the laser energy delivery device is usually discarded as soon as sparks are seen, adding to the cost of the procedure.
When the distal end of one optical fiber is juxtaposed to the proximal end of another optical fiber, laser energy that misses the core of the proximal end of the other fiber can cause overheating at the juncture. Likewise, laser energy that misses the core of the proximal end of an optical fiber encased in a laser connector can erode the optical fiber, overheat the connector and be reflected back into the laser. In both of the above examples, injury to the operator or the laser can occur, as well as premature failure of the device.
When laser energy must be delivered laterally from the axis of an optical fiber at an angle of about 60° or more, an optical fiber cannot be bent at such an angle in a confined space, as it will leak laser energy if the bend radius thereof exceeds a certain limit (about a 1 cm radius for an optical fiber with a core diameter of 200 microns). For use in a confined space, such as in tissue, or in a duct, blood vessel, hollow organ or surgically created passageway, a side-firing, fiber optic laser device, emitting energy at a 60° or greater angle from the axis of the device, is preferred.
As shown in co-owned U.S. Pat. Nos. 5,649,924; 5,437,660 and 5,242,438, the disclosures of which are fully incorporated herein by reference, a reflective metal surface, such as gold, silver, copper or a dielectric may be positioned opposite the distal end of a straight-ahead firing optical fiber to reflect laser energy at an angle of about 70° to 100° by positioning the metal surface at an angle of about 35° to 50°, respectively, from the axis of the optical fiber. Such devices can be made of medical grade stainless steel or other metal which has been plated with gold, silver, copper or other reflective material, may contain an insert of such a reflective material or can be composed entirely of the reflective material. Silver is preferred as it is almost as reflective as gold, costs less than gold and does not oxidize like copper.
Such devices are particularly well suited to the lateral reflection of wavelengths of laser energy at 300 to 1600 nm, such as from excimer, argon, KTP, diode, Nd:YAG and other lasers in an aqueous liquid medium, as such wavelengths are not highly absorbed by water.
Another solution is to bevel the distal end of an optical fiber at an angle of about 30° to 50°, preferably about 35° to 40°, most preferably at about 39° from the axis of the optical fiber, into a prism-like shape. Encasing the beveled distal end of the optical fiber inside a quartz or fused silica, closed-ended capillary tube provides the air interface opposite the beveled surface of the optical fiber which is required for total internal reflection of the laser energy to occur laterally from the axis of the optical fiber. To prevent mechanical damage to the capillary tube, the distal end portion of the beveled optical fiber and the surrounding capillary tube are preferably encased in a metal cannula, such as medical grade stainless steel.
However, back-scatter of laser energy from the target tissue and imperfections in the beveled surface of the optical fiber and the surrounding capillary tube, as well as the curvature of the capillary tube, can cause some of the energy to be emitted in other than the desired direction, which can erode the capillary tube and cause it to fracture or fail to maintain the needed air environment. Such aberrant laser energy can also overheat the non-energy emitting, back surface or sides of the capillary tube or metal cannula.
When such devices are used in industrial, scientific or military applications close to sensitive materials, or in medical applications, where sensitive structures such as nerves or blood vessels may be inadvertently struck by laser energy, even a small amount of laser energy emitted in other than the intended direction may pose an unacceptable risk. Also, a delicate industrial material or a sensitive bodily structure, such as a nerve, blood vessel or other tissue, may be damaged by contact with an overheated metal or glass portion of the device.
It is an object of the present invention to improve the laser energy delivering efficiency, reduce overheating and increase the useful life of devices that utilize an optical fiber whose distal end has been beveled at an angle of about 30° to 50° and encased in a closed-ended capillary tube to obtain the benefit of total internal reflection of laser energy of wavelengths of about 300 to 3000 nm at an angle of about 60° to 90° from the axis of the optical fiber. (See FIGS. 1-5.)
It is an object of the present invention to improve the laser energy delivery efficiency, reduce overheating and increase the useful lifetime of devices that use a reflective metal surface, inclined at an angle of about 35° to 50° opposite the distal end of an optical fiber to reflect laser energy of wavelengths of about 300 to 1400 nm at an angle of about 70° to 100° from the axis of the optical fiber. (See FIGS. 14 and 15.)
It is an object of the present invention to improve the laser energy delivery efficiency, reduce overheating and increase the useful lifetime of devices that use a reflective metal surface, inclined at an angle of about 35° to 50° opposite the distal end of an optical fiber, with a window to exclude aqueous liquids to reflect laser energy at wavelengths of about 1400 to 3000 nm at an angle of about 70° to 100° from the axis of the optical fiber. (See FIGS. 17, 18, 19a) and 19(b).)
It is an object of the present invention to avoid erosion from back-scattered laser energy, aberrant emissions of laser energy and a loss of laser energy delivery efficiency from the distal end of an optical fiber or a device in which the distal end of an optical fiber whose distal end has been beveled at an angle of about 30° to 50° and encased in a closed-ended capillary tube to obtain total internal reflection of the laser energy, using laser energy of wavelengths of about 300 to 3000 nm. (See FIGS. 16(a)-(d)).
It is an object of the present invention to improve laser energy delivery efficiency, reduce overheating and increase the useful lifetime of devices in which an optical fiber is encased in a metal or plastic cannula, using laser energy at wavelengths of about 300 to 3000 nm. (See FIGS. 6-10.)
It is an object of the present invention to improve laser energy delivery efficiency, reduce overheating and increase the useful lifetimes of devices in which the distal end of one optical fiber is juxtaposed opposite the proximal end of another optical fiber inside a metal or plastic sheath for transmission of laser energy of wavelengths of about 300 to 3000 nm. (See FIGS. 11 and 12.)
It is an object of the present invention to improve laser energy transmission efficiency, reduce overheating and increase the useful lifetimes of devices in which the proximal end of an optical fiber is contained in a connector for optically coupling the optical fiber to a source of laser energy of wavelengths of about 300 to 3000 nm, as well as to avoid the reflection of laser energy back into the source of laser energy. (See FIG. 13.)
The present invention addresses and satisfies all of the foregoing objects.